Docs module documentation outdated

[Ice2burn]

Tried to follow docs module integration docs. Project structure is old and migration instructions now is not correct, but it's fine. After all I stuck at the step 6. No matter how I try to configure new DocsProject I keep getting error:

NullReferenceException: Object reference not set to an instance of an object.
Volo.Docs.Pages.Documents.Project.IndexModel.RedirectToDefaultLanguage()

So either some configuration is missing or Docs module is broken.
Step-by-step sample project attached. Log inside Web application.
Acme.MyProject.zip

DocsProjects configuration
INSERT [dbo].[DocsProjects] ([Id], [Name], [ShortName], [Format], [DefaultDocumentName], [NavigationDocumentName], [MinimumVersion], [DocumentStoreType], [ExtraProperties], [MainWebsiteUrl], [LatestVersionBranchName]) VALUES (N'12f21123-e08e-4f15-bedb-ae0b2d939659', N'ABP framework (FileSystem)', N'abp', N'md', N'Index', N'docs-nav.json', NULL, N'FileSystem', N'{"Path":"C:\\Work\\Web\\Test\\src\\Acme.MyProject.Web\\Docs\\"}', N'/', NULL)

It correctly handles if docs-langs.json is missing, so I think the path is correct. Probably the problem is inside Docs module Index page, but I have no idea how to debug it.